function test()
{
  var quelle = new Array();
  for(var i=0;i<=3;i++) {
    quelle[i] = new Image();
  }  
  quelle[0].src = "Images/Strom_200px.jpg";
  quelle[1].src = "Images/Gas_200px.jpg";
  quelle[2].src = "Images/Waerme_200px.jpg";
  quelle[3].src = "Images/Wasser_200px.jpg";

  zaehler = zaehler + 1;
  if(zaehler > 3) zaehler = 0;
  var x = document.images[3].src = quelle[zaehler].src;
}


function Bilder()
{
  var aktiv = window.setInterval("test()", 5000); 
}